两个整数N和K.
两个整数N和K.
最后的牛群数.
			6 2
INPUT DETAILS:
There are 6 cows and the difference in group sizes is 2.
			3
OUTPUT DETAILS:
There are 3 final groups (with 2, 1, and 3 cows in them).
   6
  / \
 2   4
    / \
   1   3
6只奶牛先分成2只和4只.4只奶牛又分成1只和3只.最后有三群奶牛.